1. Field of the Invention
This invention pertains to the art of filter assemblies, and more specifically to air filter assemblies for use with internal combustion engines, such as would be used in apparatuses in the lawn care industry.
2. Description of the Related Art
Internal combustion engines ignite combined air and fuel for the combustion process. It is important that the mixture remains free from particulate contamination so as not to damage the engine components and provide for extended operation of the engine. It is known in the art to provide such engines on vegetation mowing devices, such as string trimmers and lawn mowers, it is also known to provide engines with an air filtration system for filtering debris from the flow of air entering the engine. A detailed explanation of the necessity of keeping the air-fuel mixture clean will not be given here, as it is well known in the art.
Filters are prone to clogging by debris, including the severed vegetation generated by the mower cutting action as well as additional particulate contamination such as dust, dirt and the like. As filters become saturated with the debris, it reduces the flow of air into the engine necessary for continued operation. In applications where a mowing device is used, typical amounts of debris can require frequent maintenance of the filter in order to provide the engine with a constant source of clean air. This can be cumbersome, time consuming and costly.
One common apparatus used in the lawn care industry is a string trimmer. A string trimmer is often utilized to complement other lawn care devices such as lawn mowers. String trimmers have the advantage of being able to get into small areas, where lawn mowers often cannot reach. String trimmers utilize a rotating shaft having strings positioned at a lower end thereof. When rotating, the strings have sufficient rigidity and inertia to cut vegetation such as grass, weeds, and the like. String trimmers are able to cut the vegetation growing close to rigid objects such as mailboxes and the edges of buildings because the rotating strings do not damage or cut these obstacles.
One of the problems faced by string trimmers is the generation of dust and debris by rotation of the strings. The dust and debris, as well as the cut vegetation, become airborne. In string trimmers known from the prior art, these airborne particles are often found in the vicinity of the air intake opening which supplies the necessary air to the internal combustion engine.
Even with the presence of a filter, an unacceptable amount of debris can enter the engine. Also, even if the filter is effective in preventing the passage of the material to the engine, the presence of debris against the filter can starve the engine for air and thereby limit engine performance.
One attempt to obviate the problems associated with the entry of debris is described in U.S. Pat. No. 4,838,908. The patent discloses an invention that diverts the flow of debris-filled air through a series of abrupt directional changes. In theory, the contour of the pathway and gravity work together to trap the particles prior to entry into the air intake of the internal combustion engine. However, particles are still received into to the housing.
Another invention as described in U.S. Pat. No. 4,261,302, discloses an inclined lip that upwardly deflects solid particles in the air away from the opening where the air enters for the fuel-air mixture.
U.S. Pat. No. 5,322,534 discloses a self-cleaning filter. This patent discloses a flexible filter bag in an upside-down position with its open end firmly supported. Air to be cleaned is pulled upwardly through the bag. When the air stream is shut off, the bag collapses, discharging accumulated particulate material into the space beneath it.
Still another invention as described by U.S. Pat. No. 5,947,219 discloses a vehicle having an engine and an air grill. The air grill is disclosed to be positioned away from the engine exhaust and to include air inlets that receive air to cool the engine. The patent discloses a separate air cleaner for use in combustion.
The lawn apparatuses, especially string trimmers, known in the art generally locate the air intake and filtering assembly toward the upper end of a housing so as to be away from the production of the debris. However, because the debris becomes airborne, even filtering assemblies located at the top of a lawn apparatus is subject to clogging. The present invention is directed to a lawn apparatus having a filtering assembly positioned so as to minimize clogging of the filter and to discourage debris from entering the motor housing.